Superrotation of Supergranulation: The Sun does The Wave

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Super-rotation of Supergranulation
The Sun does The Wave

• Supergranulation
• Pattern of horizontal outflows, outlined by
  network of magnetic features
• Dynamics poorly understood, but believed to
  correspond to a preferred cellular scale of
  thermal convection
• Puzzle for over 20 years Why does
  supergranulation appear to rotate faster around
  the Sun than the magnetic features and the
  plasma?
• Analysis of MDI observations shows that
  supergranulation undergoes oscillations and
  supports waves with periods of 6-9 days
• Waves are predominantly prograde, which explains
  the super-rotation of the pattern (cf.
  The Wave in a soccer stadium)
• Gizon et al., 2003, Nature 421, p.43

SOHO/MDI movie of solar supergranulation (10 day
sequence at 15 min image cadence)